Intermittent fasting, a diet trend popular worldwide for weight loss and metabolic health, may come with a hidden danger: a higher risk of heart-related deaths.
That’s the key takeaway from a new study by Indian researchers Dr Anoop Misra and Dr Ritesh Gupta, published in Diabetes & Metabolic Syndrome: Clinical Research & Reviews on August 22.
Why intermittent fasting became popular
Unlike traditional calorie-cutting diets, intermittent fasting focuses on when you eat, not how much. Popular methods include:
Time-Restricted Eating (TRE): Eating only within 6–10 hours a day.
Alternate-Day Fasting (ADF): Fasting every other day.
5:2 diet: Two days a week of very low-calorie intake.
Earlier studies showed that intermittent fasting might help with weight loss, blood sugar control, blood pressure, and even fatty liver disease. Because of this, many saw it as an easier, flexible alternative to daily calorie restriction.
Also read: Why do most heart attacks occur early morning? Cardiologist explains
Where the risk comes in
But the new warning comes from an analysis of nearly 20,000 US adults. Researchers led by Chen et al. found that people who ate all their meals within less than eight hours a day had a 135 per cent higher risk of dying from cardiovascular disease compared to those who ate within a more typical 12–14-hour window.
Importantly, this link held true across race, income levels, and lifestyle factors such as smoking. The effect was specific to heart-related deaths, not overall mortality or cancer.
The concern ties in with other studies showing that intermittent fasting, particularly strict TRE, can raise LDL cholesterol — the “bad” cholesterol that contributes to heart disease.
Other drawbacks
The review highlights several challenges with intermittent fasting:
Short-term side effects: Hunger, headaches, irritability, light-headedness.
Possible overeating: Especially junk food, during eating windows.
Muscle loss: If protein intake is inadequate, especially in older adults.
Hormonal effects: Some men reported lower testosterone; women may face menstrual changes.
Sleep and migraine issues: Seen in smaller studies.
Also read: Dangerous diets: How social media misinformation can turn fatal
The researchers also stressed that intermittent fasting is not suitable for everyone. It should be avoided or done only under medical supervision by:
- Pregnant or breastfeeding women
- People with type 1 diabetes or eating disorders
- Those with serious heart, kidney, or liver conditions.
A safer way forward
Misra and Gupta do not dismiss intermittent fasting outright. They note that moderate approaches — such as eating within a 10–12-hour window, earlier in the day — may provide benefits without the risks of extreme fasting. Such patterns may still help control calories and align better with the body’s circadian rhythm.
They also emphasize the need for:
- More long-term studies to confirm safety, especially for the heart.
- Personalized fasting plans tailored to age, health status, and culture.
- Balanced meals during eating windows, ensuring adequate protein and nutrients.
Also read: What is Mind diet? Here is what foods you should put on your plate
Not a metabolic cure
The study concludes that intermittent fasting is not a “metabolic cure” but may be a tool for some people to moderate calorie intake. However, the possible increased risk of cardiovascular death with very short eating windows is a red flag.
“Intermittent fasting should not be adopted blindly. It must be personalized, carefully monitored, and researched further to ensure that health benefits do not come at the cost of heart safety,” write Misra and Gupta.